Inkjet printers include a printhead having a plurality of inkjets. Each inkjet has a heating resistor that, in response to current, produces heat that causes the ejection of ink droplets. If the heating resistor is electrically malfunctioning, artifacts can be produced in the printed image.
U.S. Pat. No. 6,199,969 discloses several different ways of determining defective resistors in an inkjet printer, which measure test currents discharging from a capacitor.
Other applications containing arrays of circuit elements which require isolation from the driving circuitry to enable accurate monitoring of the circuit elements include lights on a scoreboard, an array of light emitting diodes in a display, or a group of relays in a switching system.